The present invention relates to a particulate dispersion or a molten product of a water-insoluble photographically useful compound, a producing method thereof, and a silver halide light-sensitive material using the same.
As a water-insoluble photographically useful compound used in the present invention, for example, dye-image-forming couplers, dye-image-providing redox compounds, stain inhibitors, antifoggants, ultraviolet absorbers, anti-fading agents, color mixing prevention agents, nucleating agents, silver halide solvents, bleach accelerators, developing agents, filter dyes and precursors thereof, dyestuffs, pigments, sensitizers, hardeners, whitening agents, desensitizers, antistatic agents, antioxidants, scavengers for oxidized developing agents, mordants, matte agents, development accelerators, development inhibitors, thermal solvents, color-tone-adjusting agents, lubricant and polymer latexes for dispersion, which are used as a medium for dispersing thereof, water-insoluble inorganic salts (such as zinc hydroxide), and membrane strength improvers, can be mentioned. Such water-insoluble photographically useful compounds are generally emulsified or dispersed into solid fine particles by mechanical force as oil-in-water dispersions (emulsions) or solid fine particles dispersions that are dispersed in water or hydrophilic colloid, and these dispersions are used for photographic emulsion layers or other layers. The above water-insoluble photographically useful compounds are described, for example, in Research Disclosure (R. D.) Nos. 17643, 18716, 307105, and 40145.
As the emulsifying method, agitation by an impeller, and milling by the use of a colloid mill, are generally used. Further, a method utilizing supersonic waves may also be employed. Such methods involve problems that only a portion of the given energy can be utilized for the dispersion, and sufficient fineness cannot be achieved. Further, there are methods, wherein colliding a liquid flow under pressure against a wall, or colliding liquid flows against each other, thereby dispersing the material finely by impact shocks or shearing forces, as in a Manton-Gaulin homogenizer. Such methods involve problems that only a portion of the given energy can be utilized for the dispersion, since dispersion is conducted generally only upon collision; the machine components are liable to be abraded, and a finer dispersion can not be attained. Further, use of a high-pressure homogenizer is disclosed, as in JP-A-6-308691 (xe2x80x9cJP-Axe2x80x9d means an unexamined published Japanese patent application), but no sufficient fine dispersion can yet be attained.
Media milling is generally used as a method to obtain a dispersion in a form of solid fine particles. The method involves problems that only a portion of the given energy can be utilized for the dispersion, and it takes much time. to make a fine dispersion.
Further, as described, for example, in U.S. Pat. Nos. 4933207 and 4957857, a method for precipitating a dispersion from a homogeneous system has been proposed, but it involves problems that salts or water miscible organic solvents have to be removed, the productivity is poor because of complicated steps, and the applicable range to the materials is limited, and, accordingly, the method has not yet been generally used. Further, a method for dividing all droplets by a porous membrane has been proposed, but this results in a problem of causing clogging or coalescence when used for a long period of time.
If the energy can be used effectively for the dispersion, it will lead to decrease in the usage of petroleum fuels and thus will help preserve the global environment.
As an example of water-insoluble photographically useful compounds, a dye-image-forming coupler can be mentioned. Usually, for photographic use, a dye-image-forming coupler, a high-boiling organic solvent (having a boiling point above 160xc2x0 C., and preferably above 175xc2x0 C. or more), and, to impart solubility, a low-boiling organic solvent (having a boiling point from 30 to 160xc2x0 C.), are mixed into a solution, and the composition and a hydrophilic colloidal solution are emulsified in the presence of a surfactant. However, since a low-boiling organic solvent is used, it is released in the environment, and requires equipment and energy to recover it. Considering mitigation of loads on the environment, and improvement of productivity, it is desirable to decrease the use of a low-boiling organic solvent. Further, as mentioned above, a surfactant is often used together as a dispersion aid. However, in conventional methods, a relatively great amount of a surfactant is used against a material to be dispersed, which results in problems, such as deterioration of the stability of the dispersion with lapse of time, formation of bubbles during the production steps or in the developing solution or waste water, an increase of viscosity when mixed with a hydrophilic colloid, and change of the photographic properties of a light-sensitive material using the same during storage.
An object of the present invention is to provide a method capable of producing an aqueous dispersion of a water-insoluble photographically useful compound at high energy efficiency, in a relatively simple step and without using a low-boiling solvent; a method capable of producing the aqueous dispersion with a reduced amount of a surfactant; as well as a method for producing a finer dispersion of a water-insoluble photographically useful compound under such conditions; dispersions obtained thereby; a coating composition containing the dispersion; and a silver halide photographic light-sensitive material using the same.
Other and further objects, features, and advantages of the invention will appear more fully from the following description, taken in connection with the accompanying drawings.